Balloon catheter with improved pushability

ABSTRACT

Balloon catheter and methods for making and using balloon catheters are disclosed. An example balloon catheter may include a proximal shaft. A midshaft may be attached to the proximal shaft. The midshaft may have an outer wall. A distal shaft may be attached to the midshaft. A balloon may be coupled to the distal shaft. An inflation lumen may be defined that extends from the proximal shaft, through the midshaft, and into the distal shaft. The inflation lumen may be in fluid communication with the balloon. A core wire may be disposed within the inflation lumen and may be attached to the midshaft.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. application Ser. No.13/475,763, filed on May 18, 2012, which claims priority under 35 U.S.C.§ 119 to U.S. Provisional Application Ser. No. 61/488,533, filed on May20, 2011, the entirety of which is incorporated herein by reference.

TECHNICAL FIELD

The present invention relates generally to catheters for performingmedical procedures. More particularly, the present invention relates toballoon catheters.

BACKGROUND

A wide variety of intracorporeal medical devices have been developed formedical use, for example, intravascular use. Some of these devicesinclude guidewires, catheters, and the like. These devices aremanufactured by any one of a variety of different manufacturing methodsand may be used according to any one of a variety of methods. Of theknown medical devices and methods, each has certain advantages anddisadvantages. There is an ongoing need to provide alternative medicaldevices as well as alternative methods for manufacturing and usingmedical devices.

BRIEF SUMMARY

The invention provides design, material, manufacturing method, and usealternatives for medical devices. An example medical device may includea balloon catheter. An example balloon catheter may include a proximalshaft. A midshaft may be attached to the proximal shaft. The midshaftmay have an outer wall. A distal shaft may be attached to the midshaft.A balloon may be coupled to the distal shaft. An inflation lumen may bedefined that extends from the proximal shaft, through the midshaft, andinto the distal shaft. The inflation lumen may be in fluid communicationwith the balloon. A core wire may be disposed within the inflation lumenand may be attached to the midshaft.

Another example balloon catheter may include a catheter shaft having adistal region and an inner wall surface defining an inflation lumen. Aballoon may be attached to the distal region. The balloon may be influid communication with the inflation lumen. A core wire may bedisposed within the inflation lumen. The core wire may be attached tothe inner wall surface at a plurality of discrete bond points.

An example method for manufacturing a catheter may include providing acatheter shaft having a distal region and an inner wall surface definingan inflation lumen and attaching a balloon to the distal region. Theballoon may be in fluid communication with the inflation lumen. Themethod may also include disposing a core wire within the inflation lumenand attaching the core wire to the inner wall surface of the cathetershaft.

The above summary of some embodiments is not intended to describe eachdisclosed embodiment or every implementation of the present invention.The Figures, and Detailed Description, which follow, more particularlyexemplify these embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention may be more completely understood in consideration of thefollowing detailed description of various embodiments of the inventionin connection with the accompanying drawings, in which:

FIG. 1 is a plan view of an example balloon catheter;

FIG. 2 is a cross-sectional view of a portion of the example ballooncatheter shown in FIG. 1;

FIG. 3 is a cross-sectional view taken through line 3-3 in FIG. 2;

FIG. 4 is an alternative cross-sectional side view of a portion of theexample balloon catheter shown in FIGS. 1-4;

FIG. 5 is a graph depicting the results of a push test for the catheterillustrated in FIGS. 1-4 compared to another catheter; and

FIGS. 6-11 illustrate some of the example method steps for manufacturingthe balloon catheter shown in FIG. 1-5.

While the invention is amenable to various modifications and alternativeforms, specifics thereof have been shown by way of example in thedrawings and will be described in detail. It should be understood,however, that the intention is not to limit the invention to theparticular embodiments described. On the contrary, the intention is tocover all modifications, equivalents, and alternatives falling withinthe spirit and scope of the invention.

DETAILED DESCRIPTION

For the following defined terms, these definitions shall be applied,unless a different definition is given in the claims or elsewhere inthis specification.

All numeric values are herein assumed to be modified by the term“about,” whether or not explicitly indicated. The term “about” generallyrefers to a range of numbers that one of skill in the art would considerequivalent to the recited value (i.e., having the same function orresult). In many instances, the terms “about” may include numbers thatare rounded to the nearest significant figure.

The recitation of numerical ranges by endpoints includes all numberswithin that range (e.g. 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4, and5).

As used in this specification and the appended claims, the singularforms “a”, “an”, and “the” include plural referents unless the contentclearly dictates otherwise. As used in this specification and theappended claims, the term “or” is generally employed in its senseincluding “and/or” unless the content clearly dictates otherwise.

The following detailed description should be read with reference to thedrawings in which similar elements in different drawings are numberedthe same. The drawings, which are not necessarily to scale, depictillustrative embodiments and are not intended to limit the scope of theinvention.

FIG. 1 is a plan view of an example catheter 10, for example a ballooncatheter. Catheter 10 may include a catheter shaft 12 having a proximalshaft portion 14, a midshaft portion 16 and a distal shaft portion 18.In some embodiments, proximal shaft portion 14 may be a metallichypotube. Midshaft portion 16 may be fitted over, fitted within, or abutproximal shaft portion 14, as appropriate. Likewise, distal shaftportion 18 may be fitted over, fitted within, or abut midshaft portion16. These are just examples as any suitable arrangement may be utilized.A hub 20 may be attached to proximal shaft portion 14. Hub 20 mayinclude one or more ports such as, for example, a port 22.

An expandable balloon 26 may be attached to distal shaft portion 18.Balloon 26 may be expanded by infusing inflation media through aninflation lumen 30, which is shown in FIG. 2. In at least someembodiments, port 22 may provide access to inflation lumen 30.Accordingly, a suitable inflation device may be attached to port 22 andinflation media may be passed through inflation lumen 30 to inflateballoon 26. Along a region of midshaft portion 16, inflation lumen 30may have an annular shape as seen in FIG. 3. This may be due to theformation of a guidewire port 28 in midshaft portion 16. Some additionaldetails regarding the formation of guidewire port 28 and/or inflationlumen 30 are provided herein.

As indicated above, guidewire port 28 may be formed in midshaft portion16. For example, guidewire port 28 may be an opening extending throughthe wall of midshaft portion 16 that provides access to a guidewirelumen 32. In the embodiment depicted in FIG. 2, guidewire port 28 ispositioned at a location that is distal to the proximal end of cathetershaft 12. When so arranged, catheter 10 may be asingle-operator-exchange or rapid-exchange catheter, which allowscatheter 10 to be used with a shorter guidewire. As such, guidewirelumen 32 may extend over only a portion of the length of catheter shaft12. For example, guidewire lumen 32 may extend along distal shaftportion 18 and part of midshaft portion 16. Other embodiments, however,are contemplated where catheter 10 is an over-the-wire catheter or fixedwire catheter. In these embodiments, guidewire lumen 32 may extend alongessentially the entire length of catheter shaft 12.

Catheters like catheter 10 may be designed to have increased orincreasing distal flexibility. This may be desirable because portions ofthe catheter 10, particularly distal portions, may need to navigatesharp bends or turns within the vasculature. When the catheter shaftincludes multiple sections or portions, however, the transition pointsbetween the sections may have a tendency to be more susceptible tokinking or buckling. For example, the transition point or points wherethe catheter shaft (e.g., catheter shaft 12) transitions from arelatively stiff proximal shaft portion (e.g., proximal shaft portion14, which may take the form of a hypotube) to a more flexible midshaftand/or distal portion (e.g., midshaft portion 16 and/or distal shaftportion 18) may be susceptible to kinking and/or buckling.

In addition, because more distal portions of the catheter 10 may bedesigned to be highly flexible, it may be challenging to push thecatheter through the vasculature in a reliable manner. In other words,increased distal flexibility, while being desirable for allowing thecatheter to navigate the tortuous anatomy, may make it more difficult to“push” the catheter through the anatomy.

In order to improve the transition in flexibility from proximal shaftportion 14 to midshaft portion 16 and/or distal shaft portion 18 and inorder to make catheter shaft 12 more “pushable” through the anatomy,catheter shaft 12 may include a core wire 33 (not shown in FIG. 2, butillustrated in FIG. 4). Core wire 33 may take the form of a wire or rodthat extends within inflation lumen 30 along an interior portion (e.g.,along an inner wall surface) of catheter shaft 12. In at least someembodiments, core wire 33 extends from proximal shaft portion 14 to aposition distally of guidewire port 28.

In order to further improve the flexibility transition and to furtherimprove the pushability of catheter 10, core wire 33 is attached to theinner surface of catheter shaft 12. For example, core wire 33 may beattached to the inner surface of midshaft portion 16. Attachment betweencore wire 33 and catheter shaft 12 may occur in a variety of differentmanners including, for example, an adhesive bond, a thermal bond, alaser bond, a weld, combinations thereof, or the like.

Core wire 33 and catheter shaft 12 may be attached at a plurality ofdiscrete bond points 35. The number of bond points 35 may vary. Forexample, core wire 33 and catheter shaft 12 may be attached at 2, 3, 4,5, 6, 7, 8, 9, 10, or more discrete bond points 35. Each of the bondpoints may be spaced from one another. As alluded to above, the discretebond points 35 may be discrete thermal bonds, laser bonds, welds,combinations thereof, or the like. Such bonding between core wire 33 andcatheter shaft 12 (e.g., midshaft portion 16) was found to increase thepushability of catheter 10. Indeed, catheter 10 was tested forpushability using a standard catheter push test and was found to haveabout a 10% increase (e.g., about 11.1%) in pushability (e.g., greaterforce transmission per unit displacement) over comparable examplecatheters that did not include a core wire that was bonded to themidshaft portion. The results of the push test for catheter 10 (alongwith comparative example catheters lacking a core wire that was bondedto the midshaft) is depicted in FIG. 5.

To facilitate the bonding between core wire 33 and catheter shaft 12, asleeve or jacket 37 may be disposed on core wire 33. Sleeve 37 mayrelatively thin wall thickness so as to have a relatively low impact onfluid flow through inflation lumen 30. In some embodiments, sleeve 37and/or core wire 33 may be longitudinally stretched, which may increasethe mechanical engagement of sleeve 37 and core wire 33 and therebyimprove the force transmission along catheter shaft 12 (e.g., fromproximal shaft portion 14 to distal shaft portion 18). Stretching sleeve37 may also thin the wall thickness of sleeve 37, which may furtherreduce any potential impact on fluid flow through inflation lumen 30.

Sleeve 37, which may be a polymer sleeve, may bond to the inner surfaceof midshaft portion 16 and, thus, bond core wire 33 to midshaft portion16. For example, a thermal bond (e.g., initiated via a laser) may allowsleeve 37 to melt and bond with midshaft portion 16 and secure core wire33. In some embodiments, sleeve 37 may include a colorant, which mayhelp improve bonding between core wire 33 and midshaft portion 16. Insome of these and in other embodiments, sleeve 37 may include aninfrared energy absorbing material. For example, sleeve 37 may includeCLEARWELD®, which is commercially available from Gentex Corporation(Carbondale, Pa.) or similar materials. The infrared absorbing materialmay be extruded (e.g., co-extruded) with the sleeve 37 material or theinfrared absorbing material may be applied to sleeve 37 (e.g., viaspraying or other suitable application methods). The use of suchmaterials may further improve the ability of core wire 33 to be bonded(e.g., welded) with midshaft portion 16. For example, application ofinfrared energy to catheter shaft 12 may allow core wire 33 to bond withmidshaft portion 16.

Core wire 33 may generally take the form of a wire or rod. In someembodiments, core wire 33 may have a substantially uniform diameter. Inother embodiments, core wire 33 may include one or more tapers or otherchanges in outer diameter. For example, the distal portion of core wire33 may taper. In addition, core wire 33 may be a singular wire having asolid cross-section. In other embodiments, core wire 33 may be tubularor include portions that are tubular. In still other embodiments, corewire 33 may include a plurality of wire filaments that may belongitudinally aligned, twisted, braided, or the like.

The materials used for core wire 33 may include a metal. This mayinclude any of the metals, to the extent appropriate, disclosed herein.For example, core wire 33 may include stainless steel, nickel-titaniumalloy, or the like. In other embodiments, core wire 33 may include arelatively stiff polymer. This may include any of the polymers, to theextent appropriate, disclosed herein. For example, core wire 33 mayinclude polyimide, polyetheretherketone, or any other suitable material.

FIGS. 6-11 illustrate some of the processing steps that may be utilizedto form catheter 10 and/or catheter shaft 12. For example, FIG. 6 showspart of midshaft portion 16. Here it can be seen that a distal end 34 ofmidshaft portion 16 may be flared or otherwise enlarged. In addition,one or more cuts or slots, for example cuts 36 a/36 b, may be formed indistal end 34 of midshaft portion 16. A tongue 38 may be defined betweencuts 36 a/36 b.

A proximal end 40 of distal shaft portion 18 may be disposed within theenlarged distal end 34 of midshaft portion 16 as shown in FIG. 7. Indoing so, tongue 38 may be pressed inward and form a shelf or ledge. Adistal inner tube 42 may be disposed within distal shaft portion 18 andmay rest upon the ledge formed by tongue 38. Distal inner tube 42 mayultimately form guidewire lumen 32 as described in more detail below.The arrangement of distal inner tube 42 relative to tongue 38, midshaftportion 16, and distal shaft portion 18 can also be seen in FIG. 8.

When suitably arranged, a first mandrel 44 may be inserted within aportion of distal shaft portion 18 and midshaft portion 16 as shown inFIG. 9. Likewise, a second mandrel 46 may be inserted within distalinner tube 42. With mandrels 44/46 in place, midshaft portion 16 anddistal shaft portion 18 may be disposed within a compression fixture 48as shown in FIG. 10. A sleeve 50 may be disposed over a region ofmidshaft portion 16 and distal shaft portion 18. Sleeve 50 may includeone or more flanking ears 52, which may aid in removal of sleeve 50 uponcompletion of the manufacturing process. Finally, heat may be applied tosleeve 50. This may include the use of a lens 54 to focus heat (e.g.,laser energy 56) onto sleeve 50 as depicted in FIG. 11. When heated,midshaft portion 16, distal shaft portion 18, and distal inner tube 42may melt together. Mandrels 44/46 can be removed, thereby defininginflation lumen 30 and guidewire lumen 32, respectively, and the resultmay be the formation of catheter shaft 12 as shown in FIGS. 1-3.

The materials that can be used for the various components of catheter 10may include those commonly associated with medical devices. Forsimplicity purposes, the following discussion makes reference tocatheter shaft 12 and other components of catheter 10. However, this isnot intended to limit the devices and methods described herein, as thediscussion may be applied to other similar tubular members and/orcomponents of tubular members or devices disclosed herein.

Catheter shaft 12 and/or other components of catheter 10 may be madefrom a metal, metal alloy, polymer (some examples of which are disclosedbelow), a metal-polymer composite, ceramics, combinations thereof, andthe like, or other suitable material. Some examples of suitable metalsand metal alloys include stainless steel, such as 304V, 304L, and 316LVstainless steel; mild steel; nickel-titanium alloy such aslinear-elastic and/or super-elastic nitinol; other nickel alloys such asnickel-chromium-molybdenum alloys (e.g., UNS: N06625 such as INCONEL®625, UNS: N06022 such as HASTELLOY® C-22®, UNS: N10276 such asHASTELLOY® C276®, other HASTELLOY® alloys, and the like), nickel-copperalloys (e.g., UNS: N04400 such as MONEL® 400, NICKELVAC® 400, NICORROS®400, and the like), nickel-cobalt-chromium-molybdenum alloys (e.g., UNS:R30035 such as MP35-N® and the like), nickel-molybdenum alloys (e.g.,UNS: N10665 such as HASTELLOY® ALLOY B2®), other nickel-chromium alloys,other nickel-molybdenum alloys, other nickel-cobalt alloys, othernickel-iron alloys, other nickel-copper alloys, other nickel-tungsten ortungsten alloys, and the like; cobalt-chromium alloys;cobalt-chromium-molybdenum alloys (e.g., UNS: R30003 such as ELGILOY®,PHYNOX®, and the like); platinum enriched stainless steel; titanium;combinations thereof; and the like; or any other suitable material.

As alluded to herein, within the family of commercially availablenickel-titanium or nitinol alloys, is a category designated “linearelastic” or “non-super-elastic” which, although may be similar inchemistry to conventional shape memory and super elastic varieties, mayexhibit distinct and useful mechanical properties. Linear elastic and/ornon-super-elastic nitinol may be distinguished from super elasticnitinol in that the linear elastic and/or non-super-elastic nitinol doesnot display a substantial “superelastic plateau” or “flag region” in itsstress/strain curve like super elastic nitinol does. Instead, in thelinear elastic and/or non-super-elastic nitinol, as recoverable strainincreases, the stress continues to increase in a substantially linear,or a somewhat, but not necessarily entirely linear relationship untilplastic deformation begins or at least in a relationship that is morelinear that the super elastic plateau and/or flag region that may beseen with super elastic nitinol. Thus, for the purposes of thisdisclosure linear elastic and/or non-super-elastic nitinol may also betermed “substantially” linear elastic and/or non-super-elastic nitinol.

In some cases, linear elastic and/or non-super-elastic nitinol may alsobe distinguishable from super elastic nitinol in that linear elasticand/or non-super-elastic nitinol may accept up to about 2-5% strainwhile remaining substantially elastic (e.g., before plasticallydeforming) whereas super elastic nitinol may accept up to about 8%strain before plastically deforming. Both of these materials can bedistinguished from other linear elastic materials such as stainlesssteel (that can also can be distinguished based on its composition),which may accept only about 0.2 to 0.44 percent strain beforeplastically deforming.

In some embodiments, the linear elastic and/or non-super-elasticnickel-titanium alloy is an alloy that does not show anymartensite/austenite phase changes that are detectable by differentialscanning calorimetry (DSC) and dynamic metal thermal analysis (DMTA)analysis over a large temperature range. For example, in someembodiments, there may be no martensite/austenite phase changesdetectable by DSC and DMTA analysis in the range of about −60 degreesCelsius (° C.) to about 120° C. in the linear elastic and/ornon-super-elastic nickel-titanium alloy. The mechanical bendingproperties of such material may therefore be generally inert to theeffect of temperature over this very broad range of temperature. In someembodiments, the mechanical bending properties of the linear elasticand/or non-super-elastic nickel-titanium alloy at ambient or roomtemperature are substantially the same as the mechanical properties atbody temperature, for example, in that they do not display asuper-elastic plateau and/or flag region. In other words, across a broadtemperature range, the linear elastic and/or non-super-elasticnickel-titanium alloy maintains its linear elastic and/ornon-super-elastic characteristics and/or properties.

In some embodiments, the linear elastic and/or non-super-elasticnickel-titanium alloy may be in the range of about 50 to about 60 weightpercent nickel, with the remainder being essentially titanium. In someembodiments, the composition is in the range of about 54 to about 57weight percent nickel. One example of a suitable nickel-titanium alloyis FHP-NT alloy commercially available from Furukawa Techno Material Co.of Kanagawa, Japan. Some examples of nickel titanium alloys aredisclosed in U.S. Pat. Nos. 5,238,004 and 6,508,803, which areincorporated herein by reference. Other suitable materials may includeULTANIUM™ (available from Neo-Metrics) and GUM METAL™ (available fromToyota). In some other embodiments, a superelastic alloy, for example asuperelastic nitinol can be used to achieve desired properties.

In at least some embodiments, portions or all of catheter shaft 12 mayalso be doped with, made of, or otherwise include a radiopaque material.Radiopaque materials are understood to be materials capable of producinga relatively bright image on a fluoroscopy screen or another imagingtechnique during a medical procedure. This relatively bright image aidsthe user of catheter 10 in determining its location. Some examples ofradiopaque materials can include, but are not limited to, gold,platinum, palladium, tantalum, tungsten alloy, polymer material loadedwith a radiopaque filler, and the like. Additionally, other radiopaquemarker bands and/or coils may also be incorporated into the design ofcatheter 10 to achieve the same result.

In some embodiments, a degree of Magnetic Resonance Imaging (MRI)compatibility is imparted into catheter 10. For example, catheter shaft12, or portions thereof, may be made of a material that does notsubstantially distort the image and create substantial artifacts (i.e.,gaps in the image). Certain ferromagnetic materials, for example, maynot be suitable because they may create artifacts in an MRI image.Catheter shaft 12, or portions thereof, may also be made from a materialthat the MRI machine can image. Some materials that exhibit thesecharacteristics include, for example, tungsten,cobalt-chromium-molybdenum alloys (e.g., UNS: R30003 such as ELGILOY®,PHYNOX®, and the like), nickel-cobalt-chromium-molybdenum alloys (e.g.,UNS: R30035 such as MP35-N® and the like), nitinol, and the like, andothers.

A sheath or covering (not shown) may be disposed over portions or all ofcatheter shaft 12 that may define a generally smooth outer surface forcatheter 10. In other embodiments, however, such a sheath or coveringmay be absent from a portion of all of catheter 10, such that cathetershaft 12 may form the outer surface. The sheath may be made from apolymer or other suitable material. Some examples of suitable polymersmay include polytetrafluoroethylene (PTFE), ethylene tetrafluoroethylene(ETFE), fluorinated ethylene propylene (FEP), polyoxymethylene (POM, forexample, DELRIN® available from DuPont), polyether block ester,polyurethane (for example, Polyurethane 85A), polypropylene (PP),polyvinylchloride (PVC), polyether-ester (for example, ARNITEL®available from DSM Engineering Plastics), ether or ester basedcopolymers (for example, butylene/poly(alkylene ether) phthalate and/orother polyester elastomers such as HYTREL® available from DuPont),polyamide (for example, DURETHAN® available from Bayer or CRISTAMID®available from Elf Atochem), elastomeric polyamides, blockpolyamide/ethers, polyether block amide (PEBA, for example availableunder the trade name PEBAX®), ethylene vinyl acetate copolymers (EVA),silicones, polyethylene (PE), Marlex high-density polyethylene, Marlexlow-density polyethylene, linear low density polyethylene (for exampleREXELL®), polyester, polybutylene terephthalate (PBT), polyethyleneterephthalate (PET), polytrimethylene terephthalate, polyethylenenaphthalate (PEN), polyetheretherketone (PEEK), polyimide (PI),polyetherimide (PEI), polyphenylene sulfide (PPS), polyphenylene oxide(PPO), poly paraphenylene terephthalamide (for example, KEVLAR®),polysulfone, nylon, nylon-12 (such as GRILAMID® available from EMSAmerican Grilon), perfluoro(propyl vinyl ether) (PFA), ethylene vinylalcohol, polyolefin, polystyrene, epoxy, polyvinylidene chloride (PVdC),poly(styrene-b-isobutylene-b-styrene) (for example, SIBS and/or SIBS50A), polycarbonates, ionomers, biocompatible polymers, other suitablematerials, or mixtures, combinations, copolymers thereof, polymer/metalcomposites, and the like. In some embodiments the sheath can be blendedwith a liquid crystal polymer (LCP). For example, the mixture cancontain up to about 6 percent LCP.

In some embodiments, the exterior surface of the catheter 10 (including,for example, the exterior surface of catheter shaft 12) may besandblasted, beadblasted, sodium bicarbonate-blasted, electropolished,etc. In these as well as in some other embodiments, a coating, forexample a lubricious, a hydrophilic, a protective, or other type ofcoating may be applied over portions or all of the sheath, or inembodiments without a sheath over portion of catheter shaft 12, or otherportions of catheter 10. Alternatively, the sheath may comprise alubricious, hydrophilic, protective, or other type of coating.Hydrophobic coatings such as fluoropolymers provide a dry lubricitywhich improves guidewire handling and device exchanges. Lubriciouscoatings improve steerability and improve lesion crossing capability.Suitable lubricious polymers are well known in the art and may includesilicone and the like, hydrophilic polymers such as high-densitypolyethylene (HDPE), polytetrafluoroethylene (PTFE), polyarylene oxides,polyvinylpyrolidones, polyvinylalcohols, hydroxy alkyl cellulosics,algins, saccharides, caprolactones, and the like, and mixtures andcombinations thereof. Hydrophilic polymers may be blended amongthemselves or with formulated amounts of water insoluble compounds(including some polymers) to yield coatings with suitable lubricity,bonding, and solubility. Some other examples of such coatings andmaterials and methods used to create such coatings can be found in U.S.Pat. Nos. 6,139,510 and 5,772,609, which are incorporated herein byreference.

The coating and/or sheath may be formed, for example, by coating,extrusion, co-extrusion, interrupted layer co-extrusion (ILC), or fusingseveral segments end-to-end. The layer may have a uniform stiffness or agradual reduction in stiffness from the proximal end to the distal endthereof. The gradual reduction in stiffness may be continuous as by ILCor may be stepped as by fusing together separate extruded tubularsegments. The outer layer may be impregnated with a radiopaque fillermaterial to facilitate radiographic visualization. Those skilled in theart will recognize that these materials can vary widely withoutdeviating from the scope of the present invention.

The entire disclosures of U.S. Pat. Nos. 6,409,863, 5,156,594,5,720,724, 6,361,529, and 6,475,187 are herein incorporated byreference.

It should be understood that this disclosure is, in many respects, onlyillustrative. Changes may be made in details, particularly in matters ofshape, size, and arrangement of steps without exceeding the scope of theinvention. The invention's scope is, of course, defined in the languagein which the appended claims are expressed.

What is claimed is:
 1. A method for manufacturing a catheter, the methodcomprising: attaching a balloon to a distal region of a catheter shaft,the catheter shaft having a guidewire port in a midshaft portionthereof, the catheter shaft having an inner wall surface defining aninflation lumen, the balloon being in fluid communication with theinflation lumen; disposing a core wire within the inflation lumen,wherein the core wire resides within the inflation lumen in the midshaftportion immediately distal of the guidewire port; and attaching the corewire to the inner wall surface of the catheter shaft by disposing asleeve on the core wire and attaching the sleeve to the inner wallsurface of the catheter shaft.
 2. The method of claim 1, wherein thesleeve includes an infrared energy absorbing material, and whereinattaching the core wire to the inner wall surface of the catheter shaftincludes irradiating the catheter shaft with infrared energy.
 3. Amethod for manufacturing a catheter, the method comprising: attaching aballoon to a distal region of a catheter shaft, the catheter shafthaving an inner wall surface defining an inflation lumen, the balloonbeing in fluid communication with the inflation lumen; forming aguidewire port in a midshaft portion of the catheter shaft; placing asingle sleeve over a core wire and disposing the core wire within theinflation lumen such that the core wire extends continuously from aproximal portion of the catheter shaft, through the midshaft portion ofthe catheter shaft, and into the distal region of the catheter shaft,wherein the core wire resides within the inflation lumen in the midshaftportion immediately distal of the guidewire port; and attaching thesleeve to the inner wall surface of the catheter shaft.
 4. The method ofclaim 3, wherein the inflation lumen extends between an outer surface ofthe sleeve and an inner surface of the midshaft portion.
 5. The methodof claim 3, wherein attaching the sleeve includes attaching the sleeveto only a single longitudinal region of the midshaft, leaving a majorityof the inflation lumen open.
 6. The method of claim 3, wherein attachingthe sleeve is performed with an adhesive.
 7. The method of claim 3,wherein attaching the sleeve is performed with a thermal bond.
 8. Themethod of claim 3, wherein attaching the sleeve is performed with alaser bond.
 9. The method of claim 3, further comprising positioning adistal end of the sleeve proximal of the guidewire port.
 10. A methodfor manufacturing a catheter, the method comprising: attaching a balloonto a distal region of a catheter shaft, the catheter shaft having aninner wall surface defining an inflation lumen, the balloon being influid communication with the inflation lumen; forming a guidewire portin a midshaft portion of the catheter shaft; placing a single polymersleeve over a core wire and disposing the core wire within the inflationlumen, wherein the core wire resides within the inflation lumen in themidshaft portion immediately distal of the guidewire port; and attachingthe polymer sleeve to the inner wall surface of the catheter shaft at aplurality of discrete bond points, wherein the sleeve is attached toonly one longitudinal region of the catheter shaft leaving a majority ofthe inflation lumen open, wherein the polymer sleeve defines at leastone of the plurality of discrete bond points.
 11. The method of claim10, wherein the inflation lumen extends between the inner wall surfaceand an outer surface of the polymer sleeve.
 12. The method of claim 10,wherein attaching the polymer sleeve to the inner wall surface of thecatheter shaft is performed with adhesive.
 13. The method of claim 10,wherein attaching the polymer sleeve to the inner wall surface of thecatheter shaft is performed with a laser.
 14. The method of claim 10,wherein attaching the polymer sleeve to the inner wall surface of thecatheter shaft is performed with thermal energy.
 15. The method of claim10, wherein the polymer sleeve is formed of infrared energy absorbingmaterial.
 16. The method of claim 10, further comprising positioning adistal end of the polymer sleeve proximal of the guidewire port.